In commercial dyeing operations in which a substrate is impregnated by padding with an aqueous dye-bath liquid, as in the conventional Thermosol process (a well-established procedure for commercial dyeing operations), the dye-impregnated substrate is commonly subjected to an intermediate drying stage prior to thermofixation or reduction of the dye. It is during this intermediate drying stage that problems with migration of the dye can occur. Migration of the dye is undesirable as the substrate becomes mottled, or unevenly shaded, thereby detracting from the appearance and the value of the dyed textile substrate.
In the conventional drying operation following the impregnating of the textile with the desired dye, the treated substrate is heated and held for a time sufficient to dry off the dye-bath liquor, conveniently at a temperature of about 100.degree. C. for convenience of rapid action by any suitable means such as hot air, infrared radiation, microwave oven, or the like. Pressures may range from below to above atmospheric pressure. It is during this convention drying operation that dye migration to the substrate surface is known to occur, said migration tending to be uncontrolled, random, and uneven, resulting in an uneven overall dyeing action, variegation, and a generally inferior quality of the finished product.
Dye migration occurs three-dimensionally; that is, in the warp and filling directions and through the fabric thickness. Migration in the warp direction does not significantly affect substrate appearance; however, migration in the filling direction and through the substrate thickness always will occur to some degree even under proper commercial drying conditions.
Many materials, including natural gums (e.g., algin) and various synthetic gums have been proposed as antimigrants to gain control over migration. (Refer to U.S. Pat. No. 3,928,676, which teaches the art of controlling migration on porous materials by using resin compositions and methods that include addition of an aluminum hydroxy salt of high molecular weight.) Many of the materials proposed in the literature are described with respect to their thickening characteristics, the terms "thickener" and "antimigrant" commonly being used synonymously. While many proposed antimigrants also find application in systems as thickeners, the more persuasive teachings available suggest that the viscosity of the dye bath per se does not have any significant effect with respect to the uncontrolled dye migration problem previously discussed. Rather, it is suggested that the function of the antimigrant is to agglomerate the dye particles in a controlled manner. The resulting agglomeration of particles imposes size constraints on the dye particles, thereby decreasing their mobility, or migration. (Refer to "Processes Involved in Particulate Dye Migration, Textile Chemist and Colorist," Vol. 7:11 pp. 192-200, 1975.)
There exists in the art a need for less expensive, more technically efficient antimigrants having enhanced compatibility with aqueous dye-bath liquor systems for the dyeing of substrates.